Begin by searing sausages in pan and add Guinness and chicken stock; cover and braise in oven at 275-300 degrees, until done through. Peel and dice potatoes and add to boiling water, cook until tender. Drain potatoes and place back in the pot. Add some butter, milk, and seasoning and mash until desired consistency. Dice the onion and sauté in a pan with half a pound of butter. When onions are translucent add in flour and make a blonde rue. Let the flour cook out and add milk in slowly then reduce heat and let simmer. Carefully remove sausages from oven, place a scoop of potatoes on center of plate and lay sausages on top and ladle on the gravy then top with green onions for garnish.